Evan Spiegel laughed and leaned back into his chair during his first sitdown interview since his iPhone app Snapchat blew up over the last month. Snapchat is #12 on the free iOS photo app charts in the U.S. and just scored some mainstream media attention in The New York Times.

Why? Snapchat is a photo-sharing app that changes privacy norms in a very novel way. The free app allows users to send others photos and control how long receivers can see them. These photos last for up to 10 seconds, before they disappear forever. If you try to take a screenshot, the app will notify the sender.

â€œIt seems odd that at the beginning of the Internet everyone decided everything should stick around forever,â€ Spiegel said. â€œI think our application makes communication a lot more human and natural.â€

By taking away the part about a photo lasting forever, it actually encourages users to share more.

â€œIâ€™m not convinced that the whole sexting thing is as big as the media makes it out to be,â€ he said. â€œI just donâ€™t know people who do that. It doesnâ€™t seem that fun when you can have real sex.â€

Spiegel said most user feedback from direct emails and Twitter posts is about sending funny faces and messages, not racy images.

But he added that the app was partially inspired by the Anthony Weiner scandal last spring and a desire to create an app with expiring data.

Snapchat user Marilyn Feldman uses the app to keep in touch with her daughter, who attends college across the country.

â€œItâ€™s subtly different even from taking a picture on my iPhone and sending that,â€ Feldman said. â€œItâ€™s more immediate and even more casual. Almost like, â€˜thinking of you.â€™ Picture of a red rose in the neighborhood. I didnâ€™t even send her a message, just a picture of the red rose, and she knew what that meant.â€

Spiegel co-founded Snapchat last spring with Bobby Murphy, who graduated from Stanford in 2010 after studying mathematical and computational science. The pair met in the Kappa Sigma fraternity house at Stanford three years ago. Spiegel would often walk down the hall to Bobbyâ€™s room at four in the morning for computer science help.

While living together, they founded Future Freshman, a college guidance site that ultimately failed to attract users and lost out to a rival with more aggressive sales and marketing. They finally gave up on Future Freshman last March, but it wouldnâ€™t be long before the duo moved on to working on Snapchat.

After kicking the idea around for a bit, Spiegel took it to his mechanical engineering class, â€˜Design and Business Factors.â€™

â€œAll the VCs and people who came through were like â€˜This is the dumbest thing ever,â€™â€ Spiegel laughed. â€œSo, obviously, I went back to Bobby and I was like, â€˜Oh, they really liked it!â€™â€

After spending the summer together in Los Angeles building a prototype, they were struggling again to attract users. Then something strange happened. The app started going viral in high schools in the Los Angeles area, including at Spiegelâ€™s cousinâ€™s school. Students were using it to pass notes and communicate during the school day.

In March, Barry Eggers, a managing director at the venture capital firm Lightspeed Venture Partners heard from his high-school daughter that the top three apps her friends were using in school were Angry Birds, Instagram, and Snapchat.

â€œThatâ€™s interesting company. Of those, the one weâ€™d never heard of was Snapchat,â€ said Jeremy Liew, Eggersâ€™ partner, who pursued Spiegel for a meeting.

â€œWe were ignoring them until we couldnâ€™t afford it,â€ Spiegel said, adding that many VCs had reached out to them about funding.

Just 25 minutes into the meeting, Liew was ready to invest, to the tune of $485,000. The team has wasted no time putting the money to use. They have hired a community manager, as well as two new engineers.

â€œHonestly I think weâ€™re building a team here but also a family,â€ Spiegel said. â€œWeâ€™ve identified some absolutely exceptional people who we really want to work with and I think thatâ€™s something thatâ€™s really important.â€

Snapchat still has a small userbase from what we can tell. Spiegel wouldnâ€™t say how large it is, but it seems that the users he does have are insanely engaged. Snapchat currently processes around 25 images every second and the team is focusing on stabilizing their iOS application. (For comparison, Instagram was processing around 25 photos a second seven months ago when it had 10 million users.)

Spiegel is also developing an Android app. And of course, theyâ€™re looking for a way to make some money off the app. While he said they donâ€™t currently have a revenue model, Spiegel said they are â€œhaving ongoing discussionsâ€ about it.

â€œWe didnâ€™t think we were ever going to raise venture capital so we were planning very early on to generate a revenue plan,â€ he said.

The success of that plan will likely rely on whether Snapchat can convince people that it is a new and useful way to communicate â€“ with or without pants.